I do the same and it works quite well. One big caveat is to make sure the US extension cord you're using is rated for 240v mains. Peak mains voltage in the US is ~170v which is why most cords in the US are rated for up to 250v. 240v countries have a peak voltage of ~340v. Most of Anker's power strips are rated for 240v mains. I use an older version of this one that has 3 USB-A ports for when I travel in the US and internationally. I do like how they made the USB ports on the newer version always on unlike mine where you have it hit a button to turn them on. That bit me in the rear twice on my last trip when the housekeeping staff decided to remove the extra key card I had left in the power slot so I could charge my stuff while I was out and when I replaced it upon returning my stuff didn't resume charging because I didn't think about pressing the button. O f course I didn't notice until the next morning when I was less than amused.

https://www.anker.com/products/a9134...41150058725526