So you and your wife have sex. It's perfectly normal, no? Then you and your wife discovers that you both have AIDs, from your wife, then to yourself. Is it lifestyle that you can blame? Or what about an AIDs-infected blood donation?
Also, your premise rests on the assumption that medical spending should be prioritized based on whether the disease was the patient's own fault. Then should be decrease spending on cures for liver or lung cancer? What about care for those involved in traffic accidents? Should there be courts finding whether the accidents were their fault and promptly withdraw funding?
Things are a lot more complicated than "American" values of responsibility and such.