To be successful on Upwork, you need to be professional.
i. Get a portfolio of the niche you are interested in.
ii. Write a 'human portfolio for each job
ii. See through your client's eyes
iv. Be determined to get the job and be excellent and extraordinary
v. Negotiate a good fee, this will also encourage you to put in your best.
If you have a great profile that looks professional or capable, your nationality does not matter.