H4 visa Epired but with a current I797A extension granted

I am in the USA, I have an expired H4 visa with an approval notice to extend the H4 form I 797A. the original H4 expired on 03/05/2020 and the I797A is good until feb23. My question is that I am unable to get the visa stamped in london because of the covid restrictions and the US Embassy in london is seeing emergency appointmets only. 1. Can I use the expired visa plus the !797A form to travel outside of the USA? Will CBP allow me bck in to the USA ans how do I get a fresh Visa Stamped into my Passport. UK citizen,

You do not need a visa to travel outside of the US. Visa is a travel document required to enter a country, in your case you will need a valid H4 visa to enter back to the US. This means you will need to get a visa appointment in the US consulate in UK (if that is where you plan to travel). You can also go to Mexico or Canada for visa stamping however there may be covid restrictions and limit visa appointment availability.