i think exactly the opposite -- Sanders respects other people and treats them with respect, so i think other foreign leaders will recognize that and treat him with respect as well. and he is firm in his convictions, and doesn't back down at all about them - he has a long political history to look at that demonstrates that.
Trump on the other hand, does not treat people with respect at all, and has already lost respect in the eyes of many foreign leaders, before even becoming president - he's not welcome in much of Europe, especially not in Belgium after the way he responded to the tragedy there, and England - maybe our closest ally in the world - has voted to ban him from setting foot on their soil. the way he openly insults China and Mexico and many other countries, i doubt very much that they have respect for him, and maybe more damning than any of that, no Arab nation will have anything to do with him whatsoever. the only way he will commandeer respect is by bullying - it is what he promises to do, after all: intimidate China into dropping our debt, or swindle them, and intimidate Mexico into building a wall for us.
Sander actually reasons with people, and presents strong coherent arguments without compromising on his principles - he's shown that he is willing & able to negotiate to get things done, without compromising his principles.
Trump insults, threatens and promises to swindle people. he's boastful and arrogant, and has shown that he's willing to compromise his principles and change his positions if doing so helps him achieve more power.
i see Sanders earning us respect around the world, and Trump earning us a lot of disrespect. in fact, Trump has already done that, and the country itself has lost international respect over the fact that he's doing so well in the nominations. if he, as a president, were to make foreign leaders listen more and pay closer attention to us, it's only because they expect us to do something stupid, bigoted and prematurely violent.