The US is a very powerful country, but when it comes to tariffs, the effect is almost mutual, unless the country the US is threatening with tariffs has a deepening economic relationship/reliance on the US. Note that Tariffs are not an economic sanction in most cases. Had it been the US wanted to use its political and economic position to sanction a country, it could have been severe, but the issue of tariffs is different.
Plus, the difference is that if USA does this, the whole world could get together and trade with each other, whereas USA would be isolationist nation that doesn't deal with anyone else. USA can't produce everything all by themselves, so they will still need other nations, and would pay more thanks to tariffs, whereas all other nations could just use each other.
Is it better to have Americans buy because they are a rich nation and selling to them would be great? Sure, but does it mean our nations will bankrupt without USA? Absolutely not, I mean economy all around the world sucked even before trump obviously, like 2008 and so forth, but we will be just trading with each other and we won't be facing that much of an issue.