I believe that only 20% of Americans own passports. American should travel more. If they traveled more (going to beach in Mexico does not count) they’d realize that we aren’t that great (relatively) and that others are catching up to us quickly.
One of the advantages America still has is that we can attract the best and the brightest. If we don’t welcome them then they’ll be staying home finding ways to compete with us. Would you rather smart foreigners worked for us or compete against us?