Question
My tree has white dome shape spots on the branches.  I have been very careful to scrape some of them off, I noticed that the white dome shapes are red under the white dome and looks like blood when you squash it.  What is it??

Answer
These are called scale insect. They live in these "domes" and suck the plant juices from the plant. Usually the limbs and if there is a heavy infestation the leaves are sticky with the extract from the scales.
You have an excellent example of wax scale. The adult females you have noticed protect themselves with a waxy outer coating as they suck plant sap. Their red eggs are deposited under the wax coat. If you can physically remove all of the adults, that is a good first step. Young wax scale, though, are camouflaged on plant stems.

The key to scale control is timing your spray to kill the crawlers just after they hatch from the eggs in April. Use an insecticide three times, at two-week intervals, starting in mid-June to control the baby scale as they emerge from under the adults.
Check with your local nursery/garden type store for an insecticide for scales. Ornamental oils sometimes work if used before the leaves emerge but I would not use them on Japanese Maple.