You do also realize that you're saying the US somehow affords more opportunity than the 26 other countries that rank above it on the Global Social Mobility Index? I don't think you've fully understood the concept here.
> Global Social Mobility Index
Look at the attributes that make up the index, they aren't objective like you're making them out to be. Also, its from the WEF, an organization that has a contentious reputation.
I'm already taxed nearly 45% of my income, pay insane property taxes on my home and car. Not to mention the goods I buy. How about the failing US government redirect its insane budget to improving things that matter, and not far away wars, foreign aid and ever-growing bureaucracy. Focus on domestic issues. Not global profiteering. People in the US, not just citizens but illegal immigrants as well, still have it pretty good compared to most places (free healthcare, EBT, housing vouchers). Thats why millions are trying to get here every year.
A country where everyone is in extreme poverty could have the top score for social mobility.