If that was true the US would have had giant import tariffs after WW2 and been promoting the absence of them in other countries. Even if you assume the US would have abolished tariffs knowing it'd cost them little immediately after WW2, they'd have put them back in the decades that followed as places like South Korea, Japan, most of Europe recovered and started exporting again. But the US didn't do that, as far as I know. American tariffs are something I didn't hear about until very recently. The US can be criticised for hypocrisy on various issues but this doesn't seem to be one of them.