I have come to this debate late but have contributed to previous discussions on Forum on this topic.
There are some well informed insurers out there who realise that CML is not the death sentence that it was 25 years ago and that it poses a very small risk of complications whilst on holiday or away on business.The responsible ones will ask you to engage in a medical screening prior to acceptance;if they offer not to cover CML then I suggest, as long as you are not travelling against medical advice, then it is not a big issue .If one has just been dx and not having reached MMR one might be more cautious.I dont know how their algorithms work but one needs to decalre all ones medical conditions because if you make claim they will want to access your medical records/conditions via you GP in UK.
Insurers will load previous heart conditions quite heavily (especially for travel to US) and even previous hypertension or a statin being taken might load it more than CML say.The biggest loading will be for age and the free insurance as part of bank or credit card deals might have cut off for age at 65 say and will certainly decline CML They also dont like previous spinal and lower back conditions.
I used World First on previous occasions but because of age guess the annual worldwide premium including USA might be up to £1000.
P.S.Some countries usually outside of Europe might insist on having Covid related cover should one contract the virus whilst in country-those countries though might be dangerous to visit at this time anyway.