There is no simple answer to that as trees come in different sizes and so need to be planted in different ways. Trees that will grow to be very big need more space when they are planted than smaller types of trees. Then there are other factors like where trees could be planted. In hard rocky areas, it would not be easy to plant trees. So there are too many variables to give a definitive answer.
about 10-18
Ireland would fit into Washington twice. Washington has total area of 71,298 square miles. Ireland has total area of 32,595 square miles.
Alberta is about 7.8 times bigger than Ireland.
Ireland would not fit into Paris. It is about 804 times bigger than Paris. Paris is about 104 square kilometres and Ireland is about 84,421 square kilometres.
Ireland is 32,525 square miles. New Zealand is 103,483 square miles. Ireland could fit in the country of New Zealand 3 times.
Afghanistan is 652,230 sq km Ireland is 70,273 sq km So it would fit almost Nine (9) times :))
lake Michigan is smaller than Ireland, you could only fit 68% of it in the lake. you could fit about 1.4 lake michigans into Ireland tho.
176
Brazil is almost 101 times the size of Ireland, being about 100.87 times larger.
245
Ireland does not fit into Holland. It is much larger. It is also bigger than the Netherlands, the country of which Holland is a region, though many people mistakenly think they are the same.
New York State is larger than Ireland, so on that basis Ireland would fit into it. As to whether you could put Ireland into it without adjusting the shape of either of them, then that would be more difficult, as their shapes are very different. Looking at it on a map, it doesn't look like it could be done.