Well, its said the gunpowder was not really good and it was old enough to catch fire. Another religion war, if it had blown the parliament house lol

Had parliament blown up and killed James I, representatives of the House of Lords and House of Commons, a huge power vacuum would have been left in their place. If the Catholics were behind the plot rather than, as some have alleged, the government orchestrating the plot to discredit and remove Catholics from positions of power, then the Catholics may have placed James' first daughter, nine year old Elizabeth, on the throne as Queen Elizabeth II. There may have been a significant power struggle before this occured, with a tug of war over who would be the best regent and adviser for the young Queen. If the Catholic advocates won, Elizabeth would have ruled the country as a Catholic Queen under the wing of Catholic advisers and regents. Her reign may have turned back the clock on the Protestant revolution within England, Wales and Scotland, making Britain a Catholic country once more. Given the pressures on a queen to marry and procreate to continue the monarchy, it is likely that Elizabeth would have been pressured into marriage with a member of one of the Catholic houses of Europe - Spain, France, Italy, Netherlands etc thus giving a substantial amount of control over Britain to a foreign power. To keep the power within Britain she may have tried to marry a noble from England or Scotland with legitimate family ties back to previous monarchs. Britain today would be vastly different. The Civil War might never have happened, or perhaps it may have happened sooner. If the Catholics maintained control of the country and put down the rising of Protestants, then Scotland and Ireland would also be different - the Jacobite Rising would never have needed to occur and Ireland would probably not have had the same religious conflicts. Britain's colonies would also probably be different - what land Britain claimed as its own would have been influenced by the diplomatic ties to whichever country Elizabeth had married into and the allegiences of Elizabeth's children. This would ultimately also affect Britain's involvement in various wars and probably the cause, effect and outcome of both the First and Second World Wars, despite these occuring over 300 years after the Gunpowder Plot.