Do most French speak another language?

We’re tackling three issues here.

First, the fact that Americans are becoming more bilingual. I have to disagree with that. Of course, compared to twenty years ago, more people today are learning foreign languages (that’s what got me to work in the US in the first place), and more people today are aware that not everybody in the world speaks English. Still, I don’t have official numbers, but the number of bilingual people is still very low.
You mention Spanish. Sure, the increasing number of Spanish speakers in the US makes the US as a country more and more bilingual, but a strange bilingualism that is made up of mostly monolingual people speaking different languages. I’m not sure that many non-Hispanic Americans are bilingual with Spanish, and as far as Hispanic Americans are concerned, I’m not sure how it’s like in the South West, but in Florida, most Hispanics seem monolingual and speak only Spanish, which is beyond my comprehension as a French person, but this is off-topic.
Now, I assume that most second generation Hispanics are more or less bilingual except in a few linguistic ghettos such as Miami, and even there educated Hispanics are bilingual.
Now, like other big immigrant waves in the past (German, Italian), it’s most likely that third, fourth and later generations Hispanic Americans will speak less and less Spanish, even if I suspect a stronger resilience of the language for various reasons that won’t be developed here.

Still, it’s important for this topic to distinguish bilingual people because they’re multicultural and bilingual people like me who have only one native language and learned a second one later.
And among the latter, the number of bilingual Americans is quite small.

What about France?
Well, the number of multicultural French people is quite low, but one can say, that almost all of them are bilingual, whether it is in the overseas territories or first and second generation immigrants.
Here again, people of foreign decent cease to be bilingual after a few generations, even faster than in the US, especially because there are no “linguistic ghetto” in France like one can find in the US.
What about regional languages?
They’re all dying to a degree or another, and except for a few exceptions (Alsacian, etc) the number of people that are bilingual by birth in those languages is negligible, even if more and more people (realizing that those languages are threatened and other reasons that are less linguistical and more political) learn them as a second or third language.

Now what about just learning foreign languages, without necessarily becoming bilingual?
Well, in France, when one reaches 6th grade (even earlier in some schools) it is compulsory to learn a foreign language (most of the time English), this language will be studied until the end of high school (that is for about 7 years), in 8th grade, most kids have to learn a second language, until 11th or 12th grade.
So basically almost everybody in France should have a basic knowledge of at least 2 foreign languages.
That’s the theory.
In practice, some kids are better at learning languages than others, some kids are better taught than others, and most important the way language teaching is designed in France plainly sucks. So in the end, very few people can actually speak foreign languages even if everybody has at least a vague concept of at least one.

Why do I say that language teaching sucks in France?
See the whole French education system is based on the learning of theory, rules, empirical things, etc. The Socratic method (which is more or less the norm in the US) is more or less inexistent. Both methods have their advantages and their inconveniences, I won’t detail them here, but the problem is that because of this philosophy of teaching and of learning, very few people in France know how to teach or to learn a language.
Teachers (or at least those who design the programs, which are decided on the national level) seem to be totally unaware that a language is something you listen to and you speak, before reading and writing. I’m saying this, because 90% of the learning process of a foreign language in a French school is about reading and writing the language, the oral part being almost inexistent.
And that gives you kids like I was, who could read English at the age of 16, but who didn’t learn how to speak it properly before actually living in an English-speaking country. And those who didn’t do that are totally unable to have a decent conversation in the language, while they can explain you grammatical points that most Americans would be clueless about.

Another problem, is that most kids, because the teaching is so theoretical, don’t comprehend that a language is something else that just a school lesson. And because of that, they won’t realize that a language is something you use, to communicate, to open your horizons and these sorts of things. They think it’s just thing you study to get a good grade (or that you don’t study because you hate the teacher and other stupid childhood mistakes like this).

Finally, no, most French people don’t secretly make fun of Americans who do their best to speak French. First of all, believe me, if they make fun of you for that, they won’t do it secretly, they’ll do it to your face.
But most of the time they won’t.
And no, when French people speak English with you in France, even if you try to speak French it’s not because they’re embarrassed or offended because you’re butchering their sacred language (how many times did I hear that?), it’s because they see you’re struggling with your French, that they think they know English better than you know French (it can be true or not) and they want to help you… and practice their English at the same time, because as mentioned before, practice is what they lack and always lacked with that language.

But even if they’ll most likely speak English with you, that doesn’t mean it’s ok to address a French person directly in English (except to say “Excuse, do you speak English?”) it’s actually extremely rude, as you are in their country, you must not assume that they speak your language.

Believe me, when a foreigner comes to me speaking directly in their language (only Americans and Spaniards do that though), they won’t get much help from me. If they speak Spanish, I won’t understand what they say, and I won’t try. If they speak English, I’ll go to the extent of pretending I don’t speak English, and/or make them understand how rude they are in the way that’s gonna make them regret to ever set foot in France.
On the other hand, if they don’t do that, if they try, if they ask nicely if I speak their language, I’ll be the most helpful person in the world.

And I’m not an exception here.