That is incorrect. The US tolerates multiple citizenship, but in my experience actively discourages the practice.
Personal anecdote: My kids were born in China. China requires citizens exiting the country have a valid visa to the country of destination. BTW, China does not recognize dual nationality. Dual US citizens cannot get a US visa, since by definition as a US citizen they don’t need one. For a period of time, up until around 2003, the US embassy in China would issue a “pro-forma” US visa aka a “fake” visa good for leaving China but not good for entering the US. One would need to leave China on the Chinese passport with the proforma visa, and then enter the US using the US passport.
First couple of years with my eldest, it was really easy to go to the US consulate, explain the situation and leave an hour later with the proforma visa. Later, they made it really difficult. You could not use US citizen services, you had to apply through the Chinese passport holder process, they would then make me wait with an impatient little child until every other case had been heard (usually 5-6 hours wait time), and then get an obstreperous civil servant grilling me and 2 year old US citizen. Mao on a pogo stick, I certainly don’t want Chinese citizenship, but it was a birthright for my kids and one that the US wasn’t going to entertain.
Lemme tell ya, my experience sucked. But was NOTHING compared with how I witnessed US civil servants treating Chinese passport holders. Holy crap, the graduate student accepted by Yale for some program being summilary denied a visa after about a 30 second interview, the blinds on the interview window was shut, and I had to watch someone who had struggled their whole life to get accepted to a US ivy league graduate school realize his life was completely fucked over in 30 seconds and 98% sure that the best course of action was to go on the roof and jump.
When I had twins, I went in to the consulate, said I was going to the US and a date straight off the plane to the Chinese consulate in LA to give up the Chinese passports. Then and only then did the US consulate agree to give me a “last chance” to never again request a pro forma passport for any of my kids.
So, IMHO, the US has a problem with dual citizenship.